1. Field of the Invention
The present invention relates to detection processing performed on a three-dimensional image, and particularly to an apparatus, method and program related to detection of a boundary surface in a three-dimensional medical image.
2. Description of the Related Art
In recent years, three-dimensional medical images (voxel data) obtained by various modalities, such as CT (Computed Tomography) and MR (Magnetic Resonance), are used in diagnosis for medical treatment. The voxel data are three-dimensional data composed of many voxels, and contain a large amount of information. However, it is not easy to extract information that is necessary for diagnosis from the large amount of information. Therefore, actual diagnosis is performed after a target region of diagnosis is extracted from the voxel data by using an imaging processing apparatus, and various kinds of image processing are performed on the extracted region.
For example, when a blood vessel on a surface of an organ, such as a heart, is a target of diagnosis, a surface representing the surface of the organ is extracted, and a region having a certain thickness with respect to the surface is set as a region of interest. Further, MIF (maximum intensity projection) processing is performed on the region of interest to generate an image in which only the blood vessel is extracted, and the generated image is used to perform diagnosis on the blood vessel.
As a method for extracting an organ, as described above, a technique in which the positions of arbitrary points in voxel data are three-dimensionally specified, and a surface including the specified points is extracted by connecting the specified points to each other has been proposed. In U.S. Patent Application Publication No. 20060181551 (Patent Document 1), first, plural are specified on a surface of an organ present in voxel data. A spherical surface circumscribing the plural specified points is assumed, and the center of gravity of the circumscribed spherical surface is assumed to be a light source. Further, each of the plural specified points is projected from the light source onto the circumscribed spherical surface to obtain projection points of the specified points. A connection relationship of sides, each connecting the projection points to each other, is obtained by two-dimensional Delaunay triangulation (Delaunay 2D), and the connection relationship between the projected specified points is applied to a connection relationship of the original specified points on the surface of the organ to define a surface. In this manner, it is possible to extract the shape of the surface of the organ.
The technique disclosed in Patent Document 1 may be appropriate to extract a structure, such as a surface of an organ, which is composed of a closed surface. However, the technique disclosed in Patent Document 1 is not appropriate to extract a surface-shaped structure, such a boundary surface. For example, the technique is not appropriate to extract a boundary surface, such as a diaphragm, which divides a lung field and an abdomen from each other, a boundary surface dividing a lung or a liver into plural segments, and a boundary surface dividing a heart into left/right atria and left/right ventricles.
For accurate recognition of the position of a lesion, it is necessary to judge the position of the lesion in each tissue by observing the position of a diaphragm or a boundary surface of the tissue. Therefore, it is essential to recognize the boundary surface of each tissue in the voxel data.